Biomedical subjects
Publications and source records attributed to A Roy.
Microbial production of L-tyrosine by direct fermentation and by enzymatic methods has been reviewed. Achievements in this regard made through recombinant DNA techniques have also been included. The review also includes biosynthesis and regulation of tyrosine.
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Reconstruction of human exposure to toxic chemicals using physiologically based pharmacokinetic (PBPK) models and biomarkers is an attractive prospect, because biomarker measurements generally provide the most direct evidence of dose. Previously it has been shown that it is possible to reconstruct short-term (30 minute) exposure to chloroform, and that it is possible in some cases to resolve the total dose between two routes of uptake (Georgopoulos et al., 1994). In this paper it is shown that it is mathematically feasible to reconstruct longer term exposures to volatile organic compounds (VOCs), using benzene as a paradigm for other VOCs, and exhaled breath concentration as a biomarker of exposure. First, it is shown that exhaled breath concentration is an appropriate biomarker for long-term exposure to benzene, since benzene accumulates in fat and is eliminated in exhaled breath. Application of a benzene PBPK model (Travis et al., 1990) showed that benzene continues to accumulate in the fat compartment for over 10 days, and consequently fat acts as an integrator of dose during this period. Second, the benzene PBPK model is used to reconstruct exposure using the maximum likelihood approach. Since no data were available for long-term exposures of this duration, "data" with a normally distributed random error and 30% coefficient of variation were generated by the PBPK model for a variety of daily exposures. It was shown that in most cases it is possible to estimate cumulative exposure within 40% of the actual values, even when the exposure concentration-time profile is unknown. The estimated exposure is found to always be an underestimate of the true exposure when the exposure concentration is assumed to be constant.
The overall prevalence of dental caries was found to be 57.47 percent in an urban slum irrespective of sex, with a maximum of 75.88 percent in the age group of 5-9 years. Habit of taking hard and sticky food, bad oral hygiene were some of the important epidemiological correlates. Fluoride content of drinking water did not show any significant role.